As a technology for improving the performance of a storage control device (referred to as a node hereinafter), Patent Literature 1 discloses a technology in which, if update data transmitted from a host is stored into the non-volatile memory area of the node, it is promptly assumed that processing relevant to the update data is completed regardless of whether the data of a storage device is updated or not. The target of this technology is a storage system of an HA (high availability) structure including a two-node cluster. Each node has a non-volatile memory, and two areas, that is, an area for storing data of its own and an area for storing data of a different node on the non-volatile memory. Each node that receives update data from a host (host computer) stores the update data into an own node data storage area on a non-volatile memory of its own, and copies the update data into a different node data storage area on a no-volatile memory of the different node. After the copy of the update data is finished, the node that received the update data informs the host of the completion of the processing.
As mentioned above, in the technology disclosed in Patent Literature 1, the completion of the processing can be reported to the host if update data is stored into the non-volatile memory before the update data is written out into the storage device. In addition, owing to the duplication of the update data achieved by the copy of the update data, even if one of the two nodes is broken down, the different node can take over the processing of the one node.